As sheet type (parallel plate structure) secondary cells, nickel-metal hydride cells (NiMH) and lithium ion secondary cells (LIB) are known. However, it is considered to be difficult to electrically repair defects of these secondary cells. This is because, after filling electrolytes, the applicable electrical stimulation is allowed only in the range of a charging operation, and a voltage of reversed polarity cannot be applied, for example. This is the same as in solid LIBs and fuel cells.
Here, solar cells are known as plate type devices. The solar cell is not a cell, but has semiconductor characteristics, and the electrical repair of defects thereof is implemented (see Patent Document 1 to Patent Document 3). The suggested repair of a solar cell is performed by electrical stimulation with a voltage source brought into contact with comb-shaped electrodes of the solar cell. The voltage is applied between adjacent comb-shaped electrodes so that a reverse bias voltage is applied to PN junctions of the solar cell. It is to be noted that in the technology described in Patent Document 2, based on the application of a reverse bias voltage while it is varied periodically (sawtooth waves, for example), a forward bias voltage of an off area is applied for only short period of time during the period in which a reverse bias voltage is applied so as to let electric charge accumulated by application of the reverse bias voltage escape.